Feb 2017 Healthy Hearing
Researchers at the University of Connecticut have developed a new test to identify a specific, potential manifestation of hidden hearing loss in individuals whose standard hearing evaluations reveal normal or close to normal findings. The test, which may one day help hearing healthcare professionals identify early stages of hearing loss, detects deficits in the binaural auditory processing system, a complex system involving both ears and the brain in locating sounds and navigating noisy environments.
New research goes beyond the audiogram to detect hidden hearing loss
This outcome is the first in a project focusing on binaural hearing conducted by Leslie R. Bernstein and Constantine Trahiotis, professors of neuroscience and surgery at the University of Connecticut. The two researchers have been colleagues for nearly 40 years and are considered leaders in the field of binaural auditory research. Bernstein and Trahiotis theorised that small neural losses for each individual ear might show only slight or even no measurable changes in some individuals’ audiograms, yet still produce a deficiency in their binaural auditory system. To test this, they studied 31 adults ages 30 to 67 with normal or near normal audiograms, by measuring binaural changes in sounds at levels of loudness that are close to those experienced in normal conversations. “The finding is that people with normal audiograms and who are fine with monaural or single ear hearing, have a deficit when it comes to binaural hearing,” Bernstein said. “We see it as sort of an early window to what is going on. If you want to catch something early, you might just want to test the binaural system.” Bernstein explained that in binaural processing, the brain compares what’s going on in the left and right ear from a series of neural connections it receives from both. “Any deficit in the left or right could have a big impact on a system that’s looking for coincident occurrence of neural firing,” he said. “It’s an unbelievable system in terms of what it calculates. If you do anything to diminish its temporal precision, then you’ll see it in tests of the binaural system.”
One of the chief complaints of people with hearing loss is that while they report that they can “hear” just fine, they have trouble understanding conversation in noisy environments—an ability that relies to a great extent on a normally-functioning binaural system. Bernstein believes his and Trahiotis’s research is another step forward in understanding the complexities of the human auditory system, which is an instrumental part of providing medical professionals with the insight they need to one day restore hearing loss. “Before you can develop ways to redress hearing deficits, it’s important to understand how the normal system works in great detail," he said. “So by understanding what the deficit might be, one might imagine future prosthetic devices to restore that particular function in a very targeted way.”
“One thing we’d like to do is make behavioral tests like these very portable,” Bernstein said. “There’s nothing about the signal generation that couldn’t be done with the computing power of a smartphone. This entire procedure could be run on standard laptop with a sound card and earphones -- nothing more elaborate than that.” But don’t expect this to be standard testing protocol at your local hearing centre anytime soon. “Under laboratory conditions with standard paradigms, my colleague and I decided to look at people who had no more than any slight hearing loss to see if these kinds of laboratory tests would reveal any types of difference between these groups. And they did. Translating this into a test that people want to use easily and effectively will take some time.”